The method of image formation using a so-called scanner system involves forming images using a scanning exposure. There are various types of recording apparatus in which use is made of scanner systems, and conventionally glow lamps, xenon lamps, mercury lamps, tungsten lamps and light emitting diodes have been used, for example, as the recording light sources in these scanner type recording devices. However, all these light sources have a low output, and there is a further disadvantage in that they have a short life expectancy. Scanners in which coherent laser light sources, for example, gas lasers such as neon-helium lasers, argon lasers and helium cadmium lasers, and semiconductor lasers, are used as light sources are used as a means of overcoming these problems.
Gas lasers have a high output but the equipment is bulky and expensive and there is a further disadvantage in that a modulator is required.
On the other hand, semiconductor lasers are small and cheap, modulation can be achieved easily, and they have a further advantage in that they have a longer life expectancy than gas lasers. However, the emission wavelengths of semiconductor lasers are, in the main, in the infrared region, and it is necessary to use sensitive materials which are photosensitive to the infrared region. However, infrared sensitive photosensitive materials have poor storage stability because of the poor stability of the infrared sensitizing dyes, they are difficult to manufacture, and they are also very poor in respect of their handling properties. Hence, a method of forming images by exposing a silver halide photosensitive material which has been spectrally sensitized in the visible region with spectrally sensitizing dyes which have good storage stability while retaining the advantages of the semiconductor laser is clearly desirable.
In one such method, second harmonics obtained by combining a laser with a wavelength conversion element consisting of a non-linear type optical material are used as light sources, as disclosed in JP-A-63-113534. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".) However, the following major limitation inevitably arises when such light sources are used. Thus, the wavelengths of the lasers which can be used are limited and so the wavelengths of the second harmonics which can be obtained are also limited and it is not possible to select the wavelengths which are most desirable from the point of view of color reproduction.
The use of silver halide grains which have a high silver chloride content in the green sensitive layer and the red sensitive layer has been proposed, in JP-A-63-18345, as a means of resolving this problem.
Further, silver halide photosensitive material containing a high silver chloride-containing emulsion having a local phase of silver bromide has been known, as is described in EP-A-0273430 (The term "EP-A" as is herein signifies an unexamined published European patent application).
However, serious unforeseen problems arise with a normal printer exposure when scanning exposures are made using silver halide emulsions which have a high silver chloride content. Thus, the color on a single print obtained using a scanning exposure differs in the parts where the scanning exposure starts from that in the parts where the scanning exposure finishes. On investigating the cause of this effect in detail it was found that the speed and gradation of the silver halide emulsion change over a very short period of time (within 1 minute) after exposure. Moreover, it was found that this change is particularly pronounced when the exposure is short and the exposure brightness is high. Hence, this does not present a problem with the conventional method of exposure where the whole surface of each print is exposed at the same time, since in this case the color changes as a whole, but in the case of a scanning exposure where the different parts of the print are exposed at different times, differences in color arise according to the position on the print and the differences which do arise are readily seen.
Hence, sensitive materials which provide good color reproduction, making up for the disadvantages of exposing apparatus in which a laser is combined with a wavelength converting element (with which the wavelength selection range is narrow and it is difficult to select the preferred wavelength for color reproduction), and with which no change occurs in respect of speed or gradation after exposure will have to be developed for use as sensitive materials for scanning exposure purposes which have a good aging stability, being spectrally sensitized in the visible region with spectrally sensitizing dyes which have good stability with respect to the passage of time.